It is known that in current integrated circuits the requirements for precision in transferring electrical values are becoming increasingly stringent. This leads to the need to provide circuits whose functionality characteristics are ever closer to those of ideal components.
FIG. 1 illustrates a conventional current mirror circuit which is formed by a differential pair of transistors Q.sub.1 and Q.sub.2 which have common-connected emitter terminals biased by a current Iee. Transistors Q.sub.3 and Q.sub.4 are further provided in order to form a feedback loop formed by the transistors Q.sub.1 -Q.sub.4. The transistor Q.sub.4 is connected, by its emitter terminal, to the supply voltage with a resistor R.sub.1 interposed; likewise, the transistor Q.sub.3 is connected, by its emitter terminal, to the supply voltage V.sub.DD with a resistor R.sub.2 interposed and its collector terminal is common-connected to the collector terminal of the transistor Q.sub.2. The collector terminal of the transistor Q.sub.3 is further connected to its base terminal, which is connected to the base terminal of the transistor Q.sub.4.
In the transistor Q.sub.1, the collector terminal is instead connected to the supply voltage. The transistor Q.sub.4 receives in input a current I1 and has a capacitor C parallel-connected to it in order to stabilize the feedback. An output branch, constituted by a transistor Q.sub.5, is connected in parallel to the branch formed by the differential pair Q.sub.1 and Q.sub.2. In particular, in the transistor Q.sub.5 the emitter terminal is connected to the supply voltage V.sub.DD, with a resistor R.sub.3 interposed, the base terminal is connected to the base terminals of the transistors Q.sub.3 and Q.sub.4, and the collector terminal is connected to the ground by a resistor Rx.
The above-described circuit solution is affected by drawbacks due to the current mirror circuit having a low output resistance and is further affected by transfer errors, i.e., mirroring errors, because the base current of the transistor Q.sub.1 can be different from the base current of the transistor Q.sub.2 and therefore can cause the current mirroring on the transistor Q.sub.5 to be inaccurate. Another source of error is due to the differences in the Early voltage between the transistors Q.sub.4 and Q.sub.5 and specifically to the voltage differences between the collector-emitter voltage of the transistor Q.sub.4 and the collector-emitter voltage of the transistor Q.sub.5.